Automated calibration of laser system and tomography system with fluorescent imaging of scan pattern

ABSTRACT

A laser system calibration method and system are provided. In some methods, a calibration plate may be used to calibrate a video camera of the laser system. The video camera pixel locations may be mapped to the physical space. A xy-scan device of the laser system may be calibrated by defining control parameters for actuating components of the xy-scan device to scan a beam to a series of locations. Optionally, the beam may be scanned to a series of locations on a fluorescent plate. The video camera may be used to capture reflected light from the fluorescent plate. The xy-scan device may then be calibrated by mapping the xy-scan device control parameters to physical locations. A desired z-depth focus may be determined by defining control parameters for focusing a beam to different depths. The video camera or a confocal detector may be used to detect the scanned depths.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/969,688 filed on Mar. 24, 2014, the entire contents of which areincorporated herein by reference.

BACKGROUND

Over the years, surgical laser systems have replaced manual surgicaltools in ophthalmic procedures. Indeed, with applications in a varietyof different procedures, surgical laser systems have become ubiquitousin eye surgery.

For instance, in the well-known procedure known as LASIK (laser-assistedin situ keratomileusis), a laser eye surgery system employingultraviolet radiation is used for ablating and reshaping the anteriorsurface of the cornea to correct a refractive condition, such as myopiaor hyperopia. Prior to ablation during LASIK, the cornea is incised withanother surgical laser system employing a non-ultraviolet, ultra-shortpulsed laser beam to create a flap to expose an underlying portion ofthe corneal bed so it can be then be ablated and reshaped withultraviolet laser beams. Afterwards, the treated portion is covered withthe flap.

Laser eye surgery systems have also been developed for cataractprocedures. These systems can be used for various surgical procedures,including for instance: (1) creating one or more incisions in the corneaor in the limbus to reshape the cornea, (2) creating one or moreincisions in the cornea to provide access for a cataract surgeryinstrument and/or to provide access for implantation of an intraocularlens, (3) incising the anterior lens capsule (anterior capsulotomy) toprovide access for removing a cataractous lens, (4) segmenting and/orfragmenting a cataractous lens, and/or (5) incising the posterior lenscapsule (posterior capsulotomy) for various cataract-related procedures.

Often, calibrating various laser surgical systems can be cumbersome,time-consuming, and more complex than desired. For example, in somesituations, the calibration may require manual calibration of thescanning systems with a calibration plate, which can be time-intensive.Thus, providing laser eye surgery systems with improved characteristicsfor system calibration and related methods would be beneficial.

SUMMARY

Accordingly, this disclosure provides laser calibration systems andrelated methods that substantially obviate one or more problems due tolimitations and disadvantages of the related art. As mentioned earlier,laser system calibration can be time-intensive, at times requiringmanual calibration of scanning systems with a calibration plate. Assuch, providing systems and methods for automatically calibrating alaser system would be beneficial.

Thus, in some embodiments, a method of calibrating a laser system with atreatment space is provided. The laser system may include a scanningsystem and a camera. The camera may comprise a sensor with sensorsurface locations. In some embodiments, the sensor may comprise an arrayof pixels and the sensor surface locations may be pixel locations. Someembodiments provide a mapping of sensor surface locations to a treatmentspace of the laser system is provided. In some embodiments, the methodmay include a step of mapping camera pixel locations to the treatmentspace. Using the scanning system, the laser system's electromagneticradiation beam may be scanned to a series of scanning locations of afluorescent material. The series of locations may be scanned by movingthe electromagnetic beam orthogonally relative to a propagationdirection of the beam. The camera may capture light that is emitted fromthe series of locations of the fluorescent material in response to thescanned electromagnetic radiation beam. Thereafter, the scanning systemmay be calibrated with the treatment space based on the series oflocations captured by the video camera, and by mapping the sensorsurface locations to the treatment space.

In some embodiments, the sensor surface locations may be mapped to thetreatment space using polynomial fitting or lookup tables. The cameramay be calibrated by using it to view a calibration plate positionedorthogonally relative to the camera at a known distance. The calibrationplate may define discrete known locations in the treatment space.Distortions of the camera may be removed based on the locations definedby the calibration plate. In some embodiments, the calibration plate maybe a calibration grid where grid intersections define discrete knownlocations in treatment space. Optionally, the calibration plate mayinclude a plurality of through holes for passing electromagneticradiation, and the plurality of through holes may define discrete knownlocations in treatment space.

In some embodiments, the scanning system includes an xy-scan device. Themethod may include a step of defining control parameters for the xy-scandevice of the scanning system to scan the laser system's electromagneticradiation beam to the series of scanning locations of the fluorescentmaterial. Thereafter, the treatment space may be mapped to the controlparameters of the xy-scan device. In some embodiments, the treatmentspace may be mapped to the control parameters of the xy-scan device withpolynomial fit or with lookup tables. The treatment space may be mappedto the control parameters of the xy-scan device with the polynomial fitand the polynomial fit may be independent of a z-depth focus in someembodiments. Optionally, the control parameters of the xy-scan devicemay be defined so as to scan the electromagnetic radiation beam of thelaser system to locations of a rectilinear grid or of a square lattice.

In some embodiments, the scanning system may include a z-scan devicethat is configured to vary a convergence depth of the electromagneticradiation beam within the treatment space. The method may include thesteps of calibrating the z-scan device of the scanning system bydefining control parameters for the z-scan device for focusing theelectromagnetic radiation beam to a series of depth locations. Thecamera or a confocal detector may be used to capture light emitted fromthe fluorescent plate at the series of depth locations in response tothe electromagnetic radiation beam focusing. Thereafter, the treatmentspace may be mapped to the control parameters of the z-scan device. Insome embodiments, a depth between the laser system and the fluorescentmaterial may be varied using a jack supporting the fluorescent material.The jack may be configured to set the depth between the laser system andthe fluorescent material. It may also be automated to vary height.

In further aspects of the invention, a laser system may be provided. Thelaser system may include an electromagnetic radiation beam sourceconfigured to output a beam along a path toward a treatment space. Itmay also include a scanning system that is configured to direct theoutputted beam to a plurality of locations in the treatment space. Thelaser system may also include a camera for capturing images of thetreatment space. A processor may be coupled with the scanning system andthe camera. The processor may be configured to calibrate the scanningsystem by scanning the laser system's electromagnetic radiation beam toa series of scanning locations of a fluorescent material. The series oflocations may be orthogonal relative to a propagation direction of theelectromagnetic radiation beam. Using the camera, the processor mayfurther capture light emitted from the series of locations of thefluorescent material in response to the scanned electromagneticradiation beam. Thereafter, the processor may calibrate the scanningsystem with the treatment space based on the series of locationscaptured by the camera.

In some embodiments, the camera may include a sensor having an array ofpixels and each pixel may have a pixel location. The processor may mapcamera pixel locations to the treatment space by using the camera toview a calibration plate positioned orthogonally relative to the cameraat a known distance. The calibration plate may include a calibrationgrid or a plurality of through holes for passing electromagneticradiation.

In some embodiments, the scanning system may include an xy-scan device.The processor may calibrate the scanning system by defining controlparameters for the xy-scan device for scanning the electromagneticradiation beam to the series of scanning locations of the fluorescentmaterial. The processor may be used to map the treatment space to thecontrol parameters of the xy-scan device with a polynomial fit, and thepolynomial fit may be independent of a z-depth focus. In someembodiments, the processor may define the control parameters of thexy-scan device to scan the laser system's electromagnetic radiation beamto locations of a rectilinear grid or a square lattice.

In some embodiments, the scanning system may include a z-scan devicethat is configured to vary the electromagnetic radiation beam'sconvergence depth within the treatment space. The processor maycalibrate the scanning system by defining control parameters for thez-scan device to focusing the electromagnetic radiation beam to a seriesof depth locations. The camera or a confocal detector may be used tocapture light emitted from the fluorescent plate at the series of depthlocations in response to focusing the electromagnetic radiation beam.The treatment space may then be mapped to the control parameters of thez-scan device. In some embodiments, the system may include a jack forsupporting the fluorescent material. The jack may be configured to setthe depth between the laser system and the fluorescent material.

In some aspects of the invention, a non-transitory computer readablestorage medium comprising a set of computer executable instructions forcalibrating a laser system with a treatment space is provided. Executionof the instructions by a computer processor may cause the processor tocarry out the steps of mapping sensor surface locations to the treatmentspace. The processor may further send instructions to the scanningsystem to scan the laser system's electromagnetic radiation beam to aseries of scanning locations of a fluorescent material. The series oflocations may be orthogonal relative to a propagation direction of theelectromagnetic radiation beam. The processor may also receive data onthe camera's capture of light emitted from the series of locations ofthe fluorescent material in response to the scanned electromagneticradiation beam. It may also calibrate the scanning system with thetreatment space based on the series of locations captured by the camera,and on the camera pixel locations mapped to the treatment space.

In some embodiments, execution of the instructions by the computerprocessor may cause the processor to further carry out a step ofcalibrating the camera by receiving camera data of a calibration platepositioned orthogonally relative to the camera at a known distance. Thecalibration plate may define discrete known locations in the treatmentspace. Thereafter, the processor may remove out distortions of thecamera based on the locations defined by the calibration plate.

In some embodiments, where the scanning system comprises an xy-scandevice, the processor may calibrate the scanning system by definingcontrol parameters for the xy-scan device to scan the laser system'selectromagnetic radiation beam to the series of scanning locations ofthe fluorescent material. Thereafter, the treatment space may be mappedto the control parameters of the xy-scan device. In some embodiments,the processor may define the control parameters of the xy-scan device soas to scan the electromagnetic radiation beam to locations of arectilinear grid or a square lattice. The scanning system may comprise az-scan device that is configured to vary a convergence depth of theelectromagnetic radiation beam within the treatment space. In that case,the processor may calibrate the scanning system by defining controlparameters for the z-scan device for focusing the electromagneticradiation beam to a series of depth locations. The processor may receivecamera data or confocal detector data of light emitted from thefluorescent plate at the series of depth locations in response tofocusing the electromagnetic beam. Thereafter, the treatment space maybe mapped to the control parameters of the z-scan device.

In some embodiments, execution of the instructions by the computerprocessor may cause the processor to further carry out the step ofvarying a depth between the laser system and the fluorescent material bysending actuation instructions to a jack supporting the fluorescentmaterial. The jack may be configured to set the depth between the lasersystem and the fluorescent material.

This summary and the following description are merely exemplary,illustrative, and explanatory, and are not intended to limit, but toprovide further explanation of the invention as claimed. Additionalfeatures, aspects, objects and advantages of embodiments of thisinvention are set forth in the descriptions, drawings, and the claims,and in part, will be apparent from the drawings and detaileddescription, or may be learned by practice. The claims are incorporatedby reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by referring to thefollowing detailed description that sets forth illustrative embodimentsusing principles of the invention, as well as to the accompanyingdrawings of which:

FIG. 1 is a schematic diagram of a laser surgery system according tomany embodiments in which a patient interface device is coupled to alaser assembly and a detection assembly by way of a scanning assemblyand a free-floating mechanism that supports the scanning assembly.

FIG. 2 is a schematic diagram of an embodiment of the laser surgerysystem of FIG. 1 .

FIG. 3 is a simplified block diagram of acts of a method of imagingand/or of modifying an intraocular target according to many embodiments.

FIGS. 4, 5, and 6 are simplified block diagrams of optional acts thatcan be accomplished in the method of FIG. 3 according to manyembodiments.

FIG. 7 is a schematic diagram of an embodiment of the laser surgerysystem of FIG. 1 .

FIG. 8 is a plan view illustrating a calibration plate that can be usedto calibrate the laser surgery system of FIG. 1 according to manyembodiments.

FIG. 9 is a schematic diagram illustrating using the calibration plateof FIG. 8 to calibrate a camera of the laser surgery system of FIG. 1 .

FIG. 10 is a schematic diagram illustrating using the calibration plateof FIG. 8 to calibrate the scanning assembly of the laser surgery systemof FIG. 1 .

FIG. 11 is a schematic diagram illustrating using a fluorescent materialto calibrate the scanning assembly of the laser surgery system of FIG. 1.

FIG. 12 is a schematic diagram illustrating using a repositionablereflective surface to calibrate the scanning assembly of the lasersurgery system of FIG. 1 .

FIG. 13 illustrates variation in intensity of a signal generated usingthe reflective surface of FIG. 12 relative to a control parameter for az-scan device of the laser surgery system of FIG. 1 .

FIG. 14 shows mapping of coordinate references from an eye spacecoordinate reference system to a machine coordinate reference system,according to many embodiments.

FIG. 15 illustrates an exemplary method for calibrating a laser systemaccording to some embodiments of the invention.

FIG. 16 is a simplified block diagram of optional acts that can beaccomplished in the method of FIG. 15 according to many embodiments.

FIG. 17 illustrates a configuration of a calibration plate that may beused to calibrate a video camera of a laser system according toembodiments of the invention.

FIG. 18 shows a look-up table summary for a video camera according tomany embodiments.

FIG. 19 shows an optical schematic of the components corresponding tothe look-up table of FIG. 18 .

FIG. 20 shows the input and output of the look-up table as shown inFIGS. 18 and 19 .

FIG. 21 shows structure and excerpt of the look-up table as shown inFIGS. 18 to 20 .

FIG. 22 shows an exemplary scan pattern produced by defined controlparameters for calibrating an xy-scan device according to someembodiments of the invention.

FIG. 23 shows an exemplary jack which may be used for determining adesired depth focus according to embodiments of the invention.

FIGS. 24A-D illustrate an exemplary method and system for calibrating az-depth of laser system according to some embodiments of the presentinvention.

DETAILED DESCRIPTION

The following description describes various embodiments of the presentinvention. For purposes of explanation, specific configurations anddetails are set forth so as to provide a thorough understanding of theembodiments. It will also, however, be apparent to one skilled in theart that embodiments of the present invention can be practiced withoutcertain specific details. Further, to avoid obscuring the embodimentbeing described, various well-known features may be omitted orsimplified in the description.

Systems for imaging and/or treating a patient's eye(s) are provided. Inmany embodiments, a free-floating mechanism provides a variable opticalpath by which a portion of an electromagnetic beam reflected from afocal point disposed within the eye is directed to a path lengthinsensitive imaging assembly, such as a confocal detection assembly. Inmany embodiments, the free-floating mechanism is configured toaccommodate movement of the patient while maintaining alignment betweenan electromagnetic radiation beam and the patient. The electromagneticradiation beam can be configured for imaging the eye, for treating theeye, and for imaging as well as treating the eye.

Referring now to the drawings in which like numbers refer to similarelements, FIG. 1 schematically illustrates a laser surgery system 10according to many embodiments. The laser surgery system 10 may include alaser assembly 12, a confocal detection assembly 14, a free-floatingmechanism 16, a scanning assembly 18, an objective lens assembly 20, anda patient interface device 22. The patient interface device 22 may beconfigured to interface with a patient 24. The patient interface device22 may be supported by the objective lens assembly 20. The objectivelens assembly 20 may be supported by the scanning assembly 18. Thescanning assembly 18 may be supported by the free-floating mechanism 16.The free-floating mechanism 16 may have a portion having a fixedposition and orientation relative to the laser assembly 12 and theconfocal detection assembly 14.

In some embodiments, the patient interface device 22 may be configuredto interface with an eye of the patient 24. For example, the patientinterface device 22 can be configured to be coupled via vacuum suctionto an eye of the patient 24 as described in co-pending U.S. patentapplication Ser. No. 14/068,994, entitled “Liquid Optical Interface forLaser Eye Surgery System,” filed Oct. 31, 2013, the entire disclosure ofwhich is incorporated herein by reference. The patient interface 22 mayinclude an optically transmissive structure which may comprise aninterface lens that is configured to be aligned with the system and anaxis of eye. The patient interface lens can be placed on the patient'seye for surgery, and the optically transmissive structure can be placedat a distance from the objective lens. In many embodiments, theoptically transmissive structure comprises a lens placed at a contactlens optical distance (hereinafter “CLopt”). The optically transmissivestructure may comprise a thickness, which may comprise a thickness ofthe contact lens, for example. In many embodiments, although theoptically transmissive structure comprising the contact lens may contactthe eye, the contact lens may be separated from the cornea with a gapextending between the lens and the vertex of the cornea such that theposterior surface of the contact lens contacts a solution comprisingsaline or a viscoelastic solution.

The laser surgery system 10 can further optionally include a baseassembly 26 that can be fixed in place or repositionable. For example,the base assembly 26 can be supported by a support linkage that isconfigured to allow selective repositioning of the base assembly 26relative to a patient and secure the base assembly 26 in a selectedfixed position relative to the patient. Such a support linkage can besupported in any suitable manner such as by a fixed support base or by amovable cart that can be repositioned to a suitable location adjacent toa patient. In many embodiments, the support linkage includes setupjoints with each setup joint being configured to permit selectivearticulation of the setup joint and can be selectively locked to preventinadvertent articulation of the setup joint, thereby securing the baseassembly 26 in a selected fixed position relative to the patient whenthe setup joints are locked.

In many embodiments, the laser assembly 12 may be configured to emit anelectromagnetic radiation beam 28. The beam 28 can include a series oflaser pulses of any suitable energy level, duration, and repetitionrate.

In many embodiments, the laser assembly 12 incorporates femtosecond (FS)laser technology. By using femtosecond laser technology, a shortduration (e.g., approximately 10⁻¹³ to 10⁻¹⁵ seconds in duration) laserpulse (with energy level in the micro joule range) can be delivered to atightly focused point to disrupt tissue, thereby substantially loweringthe energy level required to image and/or modify an intraocular targetas compared to laser pulses having longer durations.

The laser assembly 12 can produce laser pulses having a wavelengthsuitable to treat and/or image tissue. For example, the laser assembly12 can be configured to emit an electromagnetic radiation beam 28 suchas that emitted by any of the laser surgery systems described inco-pending U.S. patent application Ser. No. 14/069,044, entitled “LaserEye Surgery System,” filed Oct. 31, 2013; and U.S. patent applicationSer. No. 12/987,069, entitled “Method and System For Modifying EyeTissue and Intraocular Lenses,” filed Jan. 7, 2011, the full disclosuresof which are incorporated herein by reference. For example, the laserassembly 12 can produce laser pulses having a wavelength from 1020 nm to1050 nm. For example, the laser assembly 12 can have a diode-pumpedsolid-state configuration with a 1030 (+/−5) nm center wavelength. Asanother example, the laser assembly 12 can produce laser pulses having awavelength 320 nm to 430 nm. Further, the laser assembly 12 can includean Nd:YAG laser source operating at the 3rd harmonic wavelength (355 nm)and producing pulses having 50 pico second to 15 nano second pulseduration. Depending on the spot size, typical pulse energies used can bein the nano joule to micro joule range. The laser assembly 12 can alsoinclude two or more lasers of any suitable configuration.

The laser assembly 12 can include control and conditioning components.For example, such control components can include components such as abeam attenuator to control the energy of the laser pulse and the averagepower of the pulse train, a fixed aperture to control thecross-sectional spatial extent of the beam containing the laser pulses,one or more power monitors to monitor the flux and repetition rate ofthe beam train and therefore the energy of the laser pulses, and ashutter to allow/block transmission of the laser pulses. Suchconditioning components can include an adjustable zoom assembly and afixed optical relay to transfer the laser pulses over a distance whileaccommodating laser pulse beam positional and/or directional variabilityso as to provide increased tolerance for component variation.

In many embodiments, the laser assembly 12 and the confocal detectionassembly 14 may have fixed positions relative to the base assembly 26.The beam 28 emitted by the laser assembly 12 may propagate along a fixedoptical path through the confocal detection assembly 14 to thefree-floating mechanism 16. The beam 28 may propagate through thefree-floating mechanism 16 along a variable optical path 30, which maydeliver the beam 28 to the scanning assembly 18. In many embodiments,the beam 28 emitted by the laser assembly 12 may be collimated so thatthe beam 28 is not impacted by patient movement induced changes in thelength of the optical path between the laser assembly 12 and the scanner16. The scanning assembly 18 may be operable to scan the beam 28 (e.g.,via controlled variable deflection of the beam 28) in at least onedimension. In many embodiments, the scanning assembly 18 is operable toscan the beam 28 in two dimensions transverse to the direction ofpropagation of the beam 28 and may be further operable to scan thelocation of a focal point of the beam 28 in the direction of propagationof the beam 28. The scanned beam may be emitted from the scanningassembly 18 to propagate through the objective lens assembly 20, throughthe interface device 22, and to the eye of the patient 24.

The free-floating mechanism 16 may be configured to accommodate a rangeof movement of the patient 24 relative to the laser assembly 12 and theconfocal detection assembly 14 in one or more directions whilemaintaining alignment of the beam 28 emitted by the scanning assembly 18with the patient 24. For example, in many embodiments, the free-floatingmechanism 16 may be configured to accommodate a range movement of thepatient 24 in any direction defined by any combination of unitorthogonal directions (X, Y, and Z).

The free-floating mechanism 16 may support the scanning assembly 18 andmay provide the variable optical path 30, which may change in responseto movement of the patient 24. Because the patient interface device 22may be interfaced with the patient 24, movement of the patient 24 mayresult in corresponding movement of the patient interface device 22, theobjective lens assembly 20, and the scanning assembly 18. Thefree-floating mechanism 16 can include, for example, any suitablecombination of a linkage that accommodates relative movement between thescanning assembly 18 and, for example, the confocal detection assembly24, and optical components suitably tied to the linkage so as to formthe variable optical path 30. Optionally, the free-floating mechanism 16can be configured as described in U.S. patent application Ser. No.14/191,095 and PCT Application No. PCT/US2014/018752, filed Feb. 26,2014 and entitled “Laser Surgery System,” the entire disclosure of whichis incorporated herein by reference.

A portion of the electromagnetic radiation beam 28 may reflect from aneye tissue at the focal point and may propagate back to the confocaldetection assembly 14. Specifically, a reflected portion of theelectromagnetic radiation beam 28 may travel back through the patientinterface device 22, back through the objective lens assembly 20, backthrough (and de-scanned by) the scanning assembly 18, back through thefree-floating mechanism 16 (along the variable optical path 30), and tothe confocal detection assembly 14. In many embodiments, the reflectedportion of the electromagnetic radiation beam that travels back to theconfocal detection assembly 14 may be directed to be incident upon asensor that generates an intensity signal indicative of intensity of theincident portion of the electromagnetic radiation beam. The intensitysignal, coupled with associated scanning of the focal point within theeye, can be processed in conjunction with the parameters of the scanningto, for example, image/locate structures of the eye, such as theanterior surface of the cornea, the posterior surface of the cornea, theiris, the anterior surface of the lens capsule, and the posteriorsurface of the lens capsule. In many embodiments, the amount of thereflected electromagnetic radiation beam that travels to the confocaldetection assembly 14 may be substantially independent of expectedvariations in the length of the variable optical path 30 due to patientmovement, thereby enabling the ability to ignore patient movements whenprocessing the intensity signal to image/locate structures of the eye.

FIG. 2 schematically illustrates details of an embodiment of the lasersurgery system 10. Specifically, exemplary configurations areschematically illustrated for the laser assembly 12, the confocaldetection assembly 14, and the scanning assembly 18. As shown in theillustrated embodiment, the laser assembly 12 can include an ultrafast(UF) laser 32 (e.g., a femtosecond laser), alignment mirrors 34, 36, abeam expander 38, a half wave plate 40, a polarizer and beam dump device42, output pickoffs and monitors 44, and a system-controlled shutter 46.The electromagnetic radiation beam 28 output by the laser 32 may bedeflected by the alignment mirrors 34, 36. In many embodiments, thealignment mirrors 34, 36 may be adjustable in position and/ororientation so as to provide the ability to align the beam 28 with thedownstream optical path through the downstream optical components. Next,the beam 28 may pass through the beam expander 38, which can increasethe diameter of the beam 28. The expanded beam 28 may then pass throughthe half wave plate 40 before passing through the polarizer. The beamexiting the laser may be linearly polarized. The half wave plate 40 canrotate this polarization. The amount of light passing through thepolarizer depends on the angle of the rotation of the linearpolarization. Therefore, the half wave plate 40 with the polarizer mayact as an attenuator of the beam 28. The light rejected from thisattenuation may be directed into the beam dump. Next, the attenuatedbeam 28 may pass through the output pickoffs and monitors 44 and thenthrough the system-controlled shutter 46. By locating thesystem-controlled shutter 46 downstream of the output pickoffs andmonitors 44, the power of the beam 28 can be checked before opening thesystem-controlled shutter 46.

As shown in the illustrated embodiment, the confocal detection assembly14 can include a polarization-sensitive device such as a polarized or annon-polarized beam splitter 48, a filter 50, a focusing lens 51, apinhole aperture 52, and a detection sensor 54. A quarter wave plate 56may be disposed downstream of the polarized beam splitter 48. The beam28 received from the laser assembly 12 may be polarized so as to passthrough the polarized beam splitter 48. Next, the beam 28 may passthrough the quarter wave plate 56, thereby rotating the polarizationaxis of the beam 28. A quarter rotation may be a preferred rotationamount. After reflecting from a focal point in the eye, a returningreflected portion of the beam 28 may pass back through the quarter waveplate 56, thereby further rotating the polarization axis of thereturning reflected portion of the beam 28. After passing back throughthe quarter wave plate 56, the returning reflected portion of the beammay experience a total polarization rotation of 90 degrees so that thereflected light from the eye may be fully reflected by the polarizedbeam splitter 48. A birefringence of the cornea can also be taken intoaccount if, for example, the imaged structure is the crystalline lens.In this case, the plate 56 can be adjusted and/or configured so that thedouble pass of the plate 56 as well as the double pass of the cornea sumup to a polarization rotation of 90 degrees. Because the birefringenceof the cornea may be different from patient to patient, theconfiguration/adjustment of the plate 56 can be done dynamically so asto optimize the signal returning to the detection sensor 54. In someembodiments, the plate 56 may be rotated at an angle. Accordingly, thereturning reflected portion of the beam 28 may be polarized to be atleast partially reflected by the polarized beam splitter 48 so as to bedirected through the filter 50, through the lens 51, and to the pinholeaperture 52. The filter 50 can be configured to block wavelengths otherthan the wavelengths of interest. The pinhole aperture 52 may block anyreturning reflected portion of the beam 28 reflected from locationsother than the focal point from reaching the detection sensor 54.Because the amount of returning reflected portion of the beam 28 thatreaches the detection sensor 54 depends upon the nature of the tissue atthe focal point of the beam 28, the signal generated by the detectionsensor 54 can be processed in combination with data regarding theassociated locations of the focal point so as to generate image/locationdata for structures of the eye.

As shown in the illustrated embodiment, the scanning assembly 18 caninclude a z-scan device 58 and a xy-scan device 60. The z-scan device 58may be operable to vary a convergence/divergence angle of the beam 28and thereby change a location of the focal point in the direction ofpropagation of the beam 28. For example, the z-scan device 58 caninclude one or more lenses that are controllably movable in thedirection of propagation of the beam 28 to vary a convergence/divergenceangle of the beam 28. The xy-scan device 60 may be operable to deflectthe beam 28 in two dimensions transverse to the direction of propagationof the beam 28. For example, the xy-scan device 60 can include one ormore mirrors that are controllably deflectable to scan the beam 28 intwo dimensions transverse to the direction of propagation of the beam28. Accordingly, the combination of the z-scan device 58 and the xy-scandevice 60 can be operated to controllably scan the focal point in threedimensions, for example, within the eye of the patient.

As shown in the illustrated embodiment, a camera 62 and associated videoillumination 64 can be integrated with the scanning assembly 18. Thecamera 62 and the beam 28 may share a common optical path through theobjective lens assembly 20 to the eye. A video dichroic 66 may be usedto combine and/or separate the beam 28 with and/or from the illuminationwavelengths used by the camera. For example, the beam 28 can have awavelength of about 355 nm and the video illumination 64 can beconfigured to emit illumination having wavelengths greater than 450 nm.Accordingly, the video dichroic 66 can be configured to reflect the 355nm wavelength while transmitting wavelengths greater than 450 nm.

FIG. 3 is a simplified block diagram of acts of a method 200, accordingto many embodiments, of imaging an eye. Any suitable device, assembly,and/or system, such as that described herein, can be used to practicethe method 200. The method 200 may include using a beam source togenerate an electromagnetic radiation beam (act 202).

The method 200 may include propagating the electromagnetic radiationbeam from a beam source to a scanner along a variable optical pathhaving an optical path length that changes in response to movement ofthe eye (act 204). The method 200 may include focusing theelectromagnetic radiation beam to a focal point at a location within theeye (act 206). The method 200 may include using the scanner to scan thefocal point to different locations within the eye (act 208). The method200 may include propagating a portion of the electromagnetic radiationbeam reflected from the focal point location back along the variableoptical path to a sensor (act 210). The method 200 may include using thesensor to generate an intensity signal indicative of the intensity of aportion of the electromagnetic radiation beam reflected from the focalpoint location and propagated to the sensor (act 212).

FIGS. 4, 5, and 6 are simplified block diagrams of optional acts thatcan be accomplished as part of the method 200. For example, the method200 can include using a first support assembly to support the scanner soas to accommodate relative movement between the scanner and the firstsupport assembly so as to accommodate movement of the eye (act 214). Themethod 200 can include using a second support assembly to support thefirst support assembly so as to accommodate relative movement betweenthe first support assembly and the second support assembly so as toaccommodate movement of the eye (act 216). The method 200 can includeusing the first support assembly to support a first reflector configuredto reflect the electromagnetic radiation beam so as to propagate to thescanner along a portion of the variable optical path (act 218). Themethod 200 can include using a base assembly to support the secondsupport assembly so as to accommodate relative movement between thesecond support assembly and the base assembly so as to accommodatemovement of the eye (act 220). The method 200 can include using thesecond support assembly to support a second reflector configured toreflect the electromagnetic radiation beam to propagate along a portionof the variable optical path so as to be incident on the first reflector(act 222). The method 200 can include using the sensor to generate theintensity signal comprises passing a reflected portion of theelectromagnetic radiation beam through an aperture to block portions ofthe electromagnetic radiation beam reflected from locations other thanthe focal point location (act 224). The method 200 can include passingthe electromagnetic radiation beam through a polarization-sensitivedevice (act 226). The method 200 can include modifying polarization ofat least one of the electromagnetic radiation beam and a portion of theelectromagnetic radiation beam reflected from the focal point location(act 228). The method 200 can include using the polarization-sensitivedevice to reflect a portion of the electromagnetic radiation beamreflected from the focal point location so as to be incident upon thesensor (act 230).

FIG. 7 schematically illustrates a laser surgery system 300, accordingto many embodiments. The laser surgery system 300 includes the laserassembly 12, the confocal detection assembly 14, the free-floatingmechanism 16, the scanning assembly 18, the objective lens assembly 20,the patient interface 22, communication paths 302, control electronics304, control panel/graphical user interface (GUI) 306, and userinterface devices 308. The control electronics 304 includes processor310, which includes memory 312. The patient interface 22 is configuredto interface with a patient 24. The control electronics 304 isoperatively coupled via the communication paths 302 with the laserassembly 12, the confocal detection assembly 14, the free-floatingmechanism 16, the scanning assembly 18, the control panel/GUI 306, andthe user interface devices 308.

The scanning assembly 18 can include a z-scan device and a xy-scandevice and a camera. The laser surgery system 300 can be configured tofocus the electromagnetic radiation beam 28 to a focal point that isscanned in three dimensions. The z-scan device can be operable to varythe location of the focal point in the direction of propagation of thebeam 28. The xy-scan device can be operable to scan the location of thefocal point in two dimensions transverse to the direction of propagationof the beam 28. Accordingly, the combination of the z-scan device andthe xy-scan device can be operated to controllably scan the focal pointof the beam in three dimensions, including within a tissue of thepatient 24 such as within an eye tissue of the patient 24. The scanningassembly 18 may be supported by the free-floating mechanism 16, whichmay accommodate patient movement induced movement of the scanningassembly 18 relative to the laser assembly 12 and the confocal detectionassembly 14 in three dimensions.

The patient interface 22 is coupled to the patient 24 such that thepatient interface 22, the objective lens assembly 20, and the scanningassembly 18 move in conjunction with the patient 24. For example, inmany embodiments, the patient interface 22 employs a suction ring thatis vacuum attached to an eye of the patient 24. The suction ring can becoupled with the patient interface 22, for example, using vacuum tosecure the suction ring to the patient interface 22.

The control electronics 304 controls the operation of and/or can receiveinput from the laser assembly 12, the confocal detection assembly 14,the free-floating assembly 16, the scanning assembly 18, the patientinterface 22, the control panel/GUI 306, and the user interface devices308 via the communication paths 302. The communication paths 302 can beimplemented in any suitable configuration, including any suitable sharedor dedicated communication paths between the control electronics 304 andthe respective system components.

The control electronics 304 can include any suitable components, such asone or more processor, one or more field-programmable gate array (FPGA),and one or more memory storage devices. In many embodiments, the controlelectronics 304 controls the control panel/GUI 306 to provide forpre-procedure planning according to user specified treatment parametersas well as to provide user control over the laser eye surgery procedure.

The control electronics 304 can include a processor/controller 310 thatis used to perform calculations related to system operation and providecontrol signals to the various system elements. A computer readablemedium 312 is coupled to the processor 310 in order to store data usedby the processor and other system elements. The processor 310 interactswith the other components of the system as described more fullythroughout the present specification. In an embodiment, the memory 312can include a look up table that can be utilized to control one or morecomponents of the laser system surgery system 300.

The processor 310 can be a general purpose microprocessor configured toexecute instructions and data, such as a Pentium processor manufacturedby Intel Corporation of Santa Clara, California. It can also be anApplication Specific Integrated Circuit (ASIC) that embodies at leastpart of the instructions for performing the method according to theembodiments of the present disclosure in software, firmware and/orhardware. As an example, such processors include dedicated circuitry,ASICs, combinatorial logic, other programmable processors, combinationsthereof, and the like.

The memory 312 can be local or distributed as appropriate to theparticular application. Memory 312 can include a number of memoriesincluding a main random access memory (RAM) for storage of instructionsand data during program execution and a read only memory (ROM) in whichfixed instructions are stored. Thus, the memory 312 provides persistent(non-volatile) storage for program and data files, and may include ahard disk drive, flash memory, a floppy disk drive along with associatedremovable media, a Compact Disk Read Only Memory (CD-ROM) drive, anoptical drive, removable media cartridges, and other like storage media.

The user interface devices 308 can include any suitable user inputdevice suitable to provide user input to the control electronics 304.For example, the user interface devices 308 can include devices such as,for example, a touch-screen display/input device, a keyboard, afootswitch, a keypad, a patient interface radio frequency identification(RFID) reader, an emergency stop button, and a key switch.

System Calibration

The laser surgery system 10 can be calibrated to relate locations in atreatment space with pixels in the camera 62 and with control parametersused to control the scanning assembly 18 such that the focal point ofthe electromagnetic radiation beam can be accurately positioned withinthe intraocular target. Such calibration can be accomplished at anysuitable time, for example, prior to using the laser surgery system 10to treat a patient's eye.

FIG. 8 is a top view diagram of a calibration plate 402 that can be usedto calibrate the laser surgery system 10. In many embodiments, thecalibration plate 402 is a thin plate having an array of targetfeatures, for example, through holes 404 therein. In alternateembodiments, the calibration plate 402 is a thin plate having a field ofsmall dots as the target features. While any suitable arrangement of thetarget features can be used, the calibration plate 402 of FIG. 8 has anorthogonal array of through holes 404. Any suitable number of the targetfeatures can be included in the calibration plate 402. For example, theillustrated embodiment has 29 rows and 29 columns of the through holes404, with three through holes at each of the four comers of thecalibration plate 402 being omitted from the orthogonal array of throughholes 404.

In many embodiments, each of the through holes 404 is sized small enoughto block a suitable portion of an electromagnetic radiation beam whenthe focal point of the electromagnetic radiation beam is not located atthe through hole. For example, each of the through holes 404 can have adiameter slightly greater than the diameter of the focal point of theelectromagnetic radiation beam so as to not block any of theelectromagnetic radiation beam when the focal point is positioned at oneof the through holes 404. In the embodiment shown, the through holes 404have a diameter of 5 μm, which is sized to be used in conjunction with afocal point diameter of 1 μm.

FIG. 9 schematically illustrates using the calibration plate 402 tocalibrate the camera 62 of the laser surgery system 10. The calibrationplate 402 is supported at a known fixed location relative to theobjective lens assembly 20. In many embodiments, the objective lensassembly 20 is configured for telecentric scanning of theelectromagnetic radiation beam and the calibration plate 402 issupported to be perpendicular to the direction of propagation of theelectromagnetic radiation beam. The calibration plate 402 is disposedbetween the objective lens assembly 20 and a light source 406. The lightsource 406 is used to illuminate the calibration plate 402. A portion ofthe illumination light from the light source 406 passes through each ofthe through holes 404, thereby producing an illuminated location withinthe field of view of the camera 62 at each of the through holes 404. Alight beam 408 from each of the through holes 404 passes through theobjective lens assembly 20, through the video dichroic 66, an into thecamera 62. In many embodiments, the camera 62 includes a sensor havingan orthogonal array of pixels (e.g., in x and y directions where thecorresponding z direction is in the direction of propagation of theelectromagnetic radiation beam). In many embodiments, X and Y pixelvalues for each of the light beams 408 is used in conjunction with theknown locations of the through holes 404 relative to the objective lensassembly 20 to determine the relationship between the camera X and Ypixel values and locations in the treatment space for dimensionstransverse to the propagation direction of the electromagnetic radiationbeam.

FIG. 10 schematically illustrates using the calibration plate 402 tocalibrate the scanning assembly 18. The calibration plate 402 issupported at a known fixed location relative to the objective lensassembly 20. In many embodiments, the objective lens assembly 20 isconfigured for telecentric scanning of the electromagnetic radiationbeam and the calibration plate 402 is supported to be perpendicular tothe direction of propagation of the electromagnetic radiation beam. Thecalibration plate 402 is disposed between the objective lens assembly 20and a detector 410. The detector 410 is configured to generate a signalindicative of how much of the electromagnetic radiation beam is incidentthereon, thereby being indirectly indicative of how much of theelectromagnetic radiation beam is blocked by the calibration plate 402.For example, when the focal point of the electromagnetic radiation beamis positioned at one of the through holes 404 (as illustrated for thefocal point disposed on the right side of the detection plate 402 inFIG. 10 ), a maximum amount of the electromagnetic radiation beam passesthrough the through hole and is incident on the detector 410. Incontrast, when the focal point of the electromagnetic radiation beam isnot positioned at one of the through holes 404 (as illustrated for thefocal point disposed above the left side of the detection plate 402 inFIG. 10 ), a portion of the electromagnetic radiation beam is blockedfrom reaching the detector 410.

Control parameters for the z-scan device 58 and the xy-scan device 60are varied to locate the focal point of the electromagnetic radiationbeam at each of a suitable set of the through holes, thereby providingdata used to determine the relationship between the control parametersfor the scanning assembly 18 and the resulting location of the focalpoint of the electromagnetic radiation beam. The z-scan device 58 isoperable to vary a convergence or divergence angle of theelectromagnetic radiation beam, thereby being operable to control thedistance of the focal point from the objective lens in the direction ofpropagation of the electromagnetic radiation beam. The xy-scan device 60is operable to vary a direction of the electromagnetic radiation beam intwo dimensions, thereby providing the ability to move the focal point intwo dimensions transverse to the direction of propagation of theelectromagnetic radiation beam.

A suitable existing search algorithm can be employed to vary the controlparameters for the z-scan device 58 and the xy-scan device 60 so as toreposition the focal point to be located at each of a suitable set ofthe through holes 404. In many embodiments where the objective lensassembly 20 is configured to telecentrically scan the electromagneticradiation beam, the resulting control parameter data for the scanningassembly 18 can be used to calibrate the scanning assembly 18 relativeto directions transverse to the direction of propagation of theelectromagnetic radiation beam (e.g., x and y directions transverse to az direction of propagation of the electromagnetic radiation beam).

FIG. 11 schematically illustrates using a fluorescent material block 412to calibrate the scanning assembly 18. The fluorescent material block412 is made of a suitable fluorescent material that emits light inresponse to absorbing electromagnetic radiation. The fluorescentmaterial block 412 is supported at a fixed location relative to theobjective lens assembly 20. With the focal point of the electromagneticradiation beam disposed within the block 412, the camera 62 is used toobserve the location of the resulting fluorescent emission in the block412. The observed location of the resulting fluorescent emission can beused in conjunction with calibration data for the camera 62 to determinex and y coordinates of the associated focal point in the treatmentspace. Suitable variation in the location of the focal point within thefluorescent material block 412 and associated position data for theresulting fluorescent emissions generated via the camera 62 can be usedto calibrate the control parameters for the scanning assembly 18. Forexample, in embodiments where the objective lens assembly 20 isconfigured to telecentrically scan the focal point, the correspondingpositional data for the resulting fluorescent emissions can be used togenerate calibrated control parameters for the xy-scan device 60 forpositioning the focal point transverse to the direction of propagationof the electromagnetic radiation beam.

FIG. 12 schematically illustrates the use of a reflective member 414 tocalibrate the scanning assembly 18. The reflective member 414 issupported at a suitable plurality of known fixed distances relative tothe objective lens assembly 20. In many embodiments, the objective lensassembly 20 is configured for telecentric scanning of theelectromagnetic radiation beam and the reflective member 414 issupported to be perpendicular to the direction of propagation of theelectromagnetic radiation beam. The reflective member 414 reflects theelectromagnetic radiation beam back through the objective lens assembly20, back through the scanning assembly 18, back through thefree-floating mechanism 16, and back to the confocal detection assembly14. For a particular distance between the objective lens assembly 20 andthe reflective member 414, the z-scan device 58 can be operated to varythe distance of the focal point from objective lens assembly.Alternatively, for a particular setting of the z-scan device resultingin a particular distance of the focal point from the objective lensassembly, the distance between the objective lens assembly 20 and thereflective member 414 can be varied. As illustrated in FIG. 13 , aresulting signal 416 produced by the detection sensor 54 of the confocaldetection assembly 14 varies in intensity with variation in the distancebetween the focal point and the reflective member 414. The intensity ofthe signal 416 generated by the detection sensor 54 is maximized whenthe focal point is located at the surface of the reflective member 414,thereby maximizing the amount of reflected light that passes through thepinhole aperture 52 to reach the detection sensor 54. By determining thevalues of the control parameter for the z-scan device 58 correspondingto a suitable plurality of distances between the reflective member 414and the objective lens assembly 20, suitable calibration parameters canbe generated for use in controlling the z-scan device 58 to control thelocation of the focal point in the treatment space in the direction ofpropagation of the electromagnetic radiation beam.

In some embodiments methods and apparatus for providing adjustment tocompensate for variations in disposable elements and other attachments,tolerances in hardware and alignment, and patient anatomy. The methodsand apparatus may comprise a software look up table (hereinafter “LUT”)embodied in a tangible medium. The LUT may comprise a map of locationsof the cutting volume in order to the control of actuators that directthe ranging (target detection) and the cutting modalities. A baselineLUT can be generated for a generalized system using optical based rulesand physics, detailed modeling of components, and anchoring (one time)to a finite data set as described herein. The expected variations can bereduced into a set of finite and manageable variables that are appliedto modify the tables subsequent to the original generation of thetables. For a constructed system having constructed components withmanufacturing tolerances, fine tuning and modification of the LUTs canbe achieved thru simple modifications of the tables based on individualsystem and automated measurements. These individualized measurements ofa constructed system can be applied to variations due to one or more of:tool-to-tool variation, tool to itself variation (for example alignvariations), output attachment variations (for example disposablecontact lenses), or patient to patient (for example individual patientanatomy), and combinations thereof, for example.

In many embodiments, one or more of the following steps can be performedwith the processor and methods as described herein. For example,baseline LUT generation can be performed comprising mapping and positiondetection in order to provide actuator commands to evaluate systemoutput performance. A baseline transfer function can be generated for apatient coordinate reference system such as XYZ to detect actuators ofthe system, for example. Baseline LUT generation can be performed to mapcutting to actuators. A transfer function can be generated for XYZ tocutting actuators, for example. Baseline LUTs (transfer functions) canbe generated via model (ray trace), data, or a combination, for example.The baseline LUTs can be modified given variations in the system,disposable, eye, application, for example. The baseline LUT modificationmay comprise an adjustment to the baseline LUT, for example. Thebaseline LUT modification may comprise a software (hereinafter “SW”)adjustment to compensate for hardware (hereinafter “HW”) variations, forexample. The LUT modification as described herein can extend surgicalvolume, so as to treat the cornea, the limbus and the posterior capsule,either in lateral extent, axial extent, and resolution, for example. TheLUT methods and apparatus can enable switching in tools for calibrationand other optical components to accessorize—output attachments, forexample. The LUT can be set up so that the system is capable ofmeasuring location of attachments at two surfaces and then canaccurately place cuts in targeted material volume based on modifying thebaseline LUT using this the locations of the two surfaces, for example.The LUTS can provide more cuts ranging from lens, capsule, cornealincisions for cataract, cornea flaps, for example. The differentsub-systems as described herein can have separate LUTS, which can becombined with calibration process as described herein, for example.

Whether alternatively or in combination, the same sub-system can be usedfor both ranging and cutting. The UF system can be used at a low powerlevel to find surfaces and then used at high power for cutting, forexample. The LUTs can be used such that the location mode differs fromthe cutting mode. In some instances, the cut locations can differ basedon changes with power level, and the cut location may not occur at focuswhen the energy per pulse substantially exceeds the threshold amount ofenergy.

In many embodiments, the LUTs of the methods and apparatus as describedherein follow these principles. The baseline LUT can generated by raytracing and data anchoring using specific tooling, for example. In manyembodiments, each optically transmissive structure of the patientinterface, such as a lens, is read by the system to determine itsthickness and location. These numbers can be used to modify the LUTS toattain <100 μm accuracy, for example.

In many embodiments, the LUTs of the methods and apparatus as describedherein are also modified to account for alignment tilts, contact lensmounting, contact lens variations so as to achieve <100 μm accuracy oncuts, for example. In many embodiments, a bubbles in plastic flatnesstest with the calibration apparatus as described herein generates offsetand tilt adjustments of baseline UF LUT.

In many embodiments, the baseline component specifications may be lessthan ideal for delivering an appropriate system performance, and thefinal performance can be refined using SW corrections and factors basedon the components of the individual system which can be determined fromoptically-grounded data-anchored baseline LUTs further modified forenhanced performance, for example.

A feedback loop can be used to build the enhanced or modified LUTs forthe individual laser system, for example. The feedback methods andapparatus as described herein can allow SW adjustments based on LUTs andother SW factors that may not be corrected with hardware alignment, forexample.

The LUTs and the methods an apparatus configured to modify the look uptables so as to enhance system performance can provide an improvementwithin the 3D surgical volume as described herein. The methods andapparatus as described herein can provide improved surgery for morepatients with a level of high performance. The methods and apparatussuch as those described herein can provide high performance usingoff-the-shelf components, such as high-volume, low-cost components tomake surgical procedures available to greater numbers of patients.

FIG. 14 shows mapping of coordinate references from an eye spacecoordinate reference system 150 to a machine coordinate reference system151 so as to coordinate the machine components with the physicallocations of the eye. Physical coordinates of the eye may be mapped tomachine coordinates of the components as described herein. The eye spacecoordinate reference system 150 may comprise a first X dimension 152,for example an X axis, a second Y dimension 154, for example a Y axis,and a third Z dimension 156, for example a Z axis. Optionally, thecoordinate reference system of the eye may comprise one or more of manyknown coordinate systems such as polar, cylindrical or Cartesian. Inmany embodiments, the reference system 150 comprises a right handedtriple with the X axis oriented in a nasal temporal direction on thepatient, the Y axis oriented superiorly on the patient and the Z axisoriented posteriorly on the patient. In many embodiments, thecorresponding machine coordinate reference system 151 comprises a firstX′ dimension 153, a second Y′ dimension 155, and a third Z′ dimension157 generally corresponding to machine actuators, and the coordinatereference system of the machine may comprise one or more of many knowncoordinate systems such as polar, cylindrical or Cartesian, andcombinations thereof, for example.

The machine coordinate reference 151 may correspond to locations of oneor more components of a laser system. The machine coordinate referencesystem 151 may comprise a plurality of machine coordinate referencesystems. The plurality of machine coordinate references system s maycomprise a coordinate reference system for each subsystem, for example.The axes of the machine coordinate reference system may be combined inone or more of many ways. In some embodiments, the locations of thecomponents of the laser system may be combined in order to map theplurality of machine coordinate reference systems to the coordinatereference system 150 of the eye.

FIG. 15 illustrates a simplified block diagram of acts of a method 100for calibrating a laser system. The laser system may include a videocamera, an xy-scan device for scanning an electromagnetic radiation beamto locations orthogonal to the beam's propagation and a z-scan devicefor focusing a focal point of an electromagnetic radiation beam todifferent distances from the laser system. At step 102, the video cameramay be calibrated with coordinates in the treatment space. At step 104,a xy-scan device may be calibrated with the treatment space and at step106, the z-scan device may be calibrated with the treatment space.

FIG. 16 shows simplified block diagrams of optional acts that can beused to accomplished some or all steps of the method 100. For example,the video camera may be calibrated 102 with the treatment space byproviding a calibration plate to a field of view of the video camera108. The video camera imaging system may use a telecentric lens toprovide and orthographic view of the calibration plate. By viewing acalibration plate, the video camera image data may be processed toremove distortions in the video camera system 110. At step 112, thevideo camera may be calibrated with the treatment space 102 by mappingthe video camera pixel locations to locations in the treatment space.The mapping may be primarily a two-dimensional mapping of Xm, Ym to X,Y. Because of the large depth of field of the imaging path and thetelecentric form, the Z location may remain unchanged for the range of Zfor which the image is in focus. In some embodiments, the camera can bea suitable imaging device for any silicon based detector array of theappropriately sized format. A video lens may form an image onto a cameradetector array while optical elements provide polarization control andwavelength filtering respectively. An aperture or iris provides controlof imaging and therefore depth of focus and depth of field andresolution. A small aperture may provide the advantage of large depth offield that aids in the patient docking procedure. In some instances, thevideo camera image sensor may comprise X and Y pixels, Pix X and Pix Y,respectively. The dimension 153 of the machine coordinate reference 151may correspond to X pixels of the video camera. The dimension 155 maycorrespond to Y pixels of the camera. In some embodiments, the videocamera pixel locations may be mapped using a system specific look uptable to generate pixel locations corresponding to the treatment space.Optionally, polynomial fitting may be used to map pixel locations tophysical locations in the treatment space.

FIG. 17 illustrates an exemplary calibration plate that comprises acalibration grid 1700. The calibration grid 1700 may define knownlocations in the treatment space. In some situations, the spacing and/orintersections 1710 of the grid may define the know locations. In otherembodiments, the calibration plate shown in FIG. 8 may be used forcalibrating the video camera system. After distortions of the videocamera system are removed, polynomial or other fitting such as look uptables can be used to map video camera pixel locations to physicallocations in the treatment space. In some embodiments, computeralgorithms may be used to automatically locate grid intersections 1710or the through holes 404 of a calibration plate.

FIG. 18 shows an exemplary look up table 330 for a video camera. Thelook up table 330 may comprise a plurality of discrete input values 332over a range, for example, four values such as X, Y, Z of patientcoordinate reference system and distance CL of the lower surface of thelens, and a plurality of discrete output values 334. The X and Y valuesof the eye can range from −9 to 9 mm, in 1 mm increments, for example.The Z value can range from 6 to 10 mm in 1 mm increments, for example.The CL value can range from −1 to 1 mm in 0.5 mm increments, forexample. These four dimensional input values can be input into processorsystem and an output machine value provide for each combined input. Theoutput values 334 of the look up table can be provided as Pixel X, PixelY, and the range of Pixel X and Pixel Y can each be from about −543pixels to about 543 pixels. The output and input mapping process can beswitched. The video system is a measurement device used to find intendedsurfaces. The video system is also used as target aid for the user toplace cuts. In these ways, the values of Pixel X and Pixel Yaredetermined using the video image. The values of Pixel X and Pixel Yalong with either assumptions or measurements made for Z and CL are usedas input values to generate output values for X, Y, and Z for thelocation of the intended targeted structure.

The data for each look up table can be interpolated, for example withknown interpolation methods. For example, the interpolation may compriselinear interpolation based on values of closest neighbors provided tothe look up table. The look up table can be extrapolated to extend theranges.

The look up tables as described herein are provided according toexamples, and a person of ordinary skill in the art will recognize manyalternatives and variations.

FIG. 19 shows an optical schematic of the components corresponding tothe look up table of FIG. 18 . The optical system forms an image on thecamera array comprising x pixels at x pixel locations (hereinafter “PixX”) and y pixels at y pixel locations (hereinafter Pix Y). The image isformed with a plurality of fixed focus lenses. The image beam passesthrough an aperture stop located between the fixed focus lenses toarrive at the sensor array. A field stop is provided along with anotherfixed focus lens optically coupled to the objective lenses. The patientinterface and distances are described herein.

FIG. 20 shows input and output of the look up table as in FIGS. 18 and19 . The input comprises the measured Pix X and Pix Y coordinatereferences of the CCD array. The input may also comprise the Z focuslocation of the eye, and the CLopt and CLth parameters. The outputcomprises the X and Y coordinate references of the eye at the input Zdepth.

FIG. 21 shows the structure of the look up table as in FIGS. 18 to 20 .Although a low resolution table is shown, the high resolution table canreadily be constructed by a person of ordinary skill in the art based onthe teachings described herein. The structure of the table comprises aheader and a body comprising columns of the table.

The header may comprise the input and output parameters for thewavelength of the video imaging system. The parameters may comprise theX, Y and Z locations of the imaging system within the eye and theparameters may comprise the corresponding X pixels (Pix X) and Y pixels(Pix Y). The header may comprise coordinate reference locationscorresponding to tissue structures of the eye, such as the iris or thelimbus, for example. The coordinate reference locations may comprise alocation within the eye along the axis of the system at coordinates X=0,Y=0 and Z=8 mm, for example. The corresponding mapped X and Y pixelcoordinates for X=5 mm and Y=5 mm can be provided at pixel coordinatelocations of approximately 303 pixels, respectively, for example. One ofthe purposes of the header is to provide a sample of key points withinthe look up table. These key points may be compared to multipleexecutions of the model to generate the look up table. These key pointscan be used as watch points to gain an overview of the performance ofthe model run and can be used to determine the health or veracity of thelook up table.

The body of the look up table may comprise the Pixel X, Pixel Y, Z,CLopt, Clth, input parameters. The output of the look up table maycomprise the output X and Y locations for each input record, forexample. The corresponding diameter of the spot can be provided at eachlocation in pixels, and a logic flag can be provided for each location.The logic flag may comprise one or more of many logic signals, and maycorrespond to whether the image of tissue is to be provided at thelocation, or whether the focus of the treatment beam at the mapped X Pixand Y Pix location is suitable for treatment, for example.

Returning to FIG. 16 , in some embodiments, an xy-scan device may becalibrated per the calibration of the video camera with the treatmentspace. In some embodiments, a xy-scan device of a laser scanning systemmay be calibrated 104 with the treatment space by first defining controlparameters for scanning an electromagnetic radiation beam to a series ofXY locations 114. An electromagnetic radiation beam may be scanned perthe defined control parameters and the calibrated video camera may beused to capture the scan locations 116. Thereafter, the treatment spacemay be mapped to the control parameters of the xy-scan device 118.

The movable components of the laser delivery system may comprise a Xgalvo mirror capable of moving an angular amount Xm, and a Y galvomirror capable of moving an angular amount Y_(m). The dimension 153 ofmachine coordinate reference system 151 may correspond to movement ofthe X galvo mirror. The dimension 155 of the machine coordinatereference system 151 may correspond to movement of the Y galvo mirror.

In some embodiments, the defined control parameters may be a voltage foractuating the X galvo mirror and the Y galvo mirror. In someembodiments, a voltage space grid may be defined for actuating the Xgalvo mirror and Y galvo mirror to a plurality of XY locations. In someembodiments, the control parameters may be defined to scan a beam usingthe xy-scan device to locations of a rectilinear grid or a squarelattice, as shown in FIG. 22 . For example, the X galvo mirror may bedriven by incremental increases in a voltage through a voltage range.Thereafter, the voltage for driving the Y galvo mirror may be increasedby an incremental amount and the X galvo mirror may then be scannedthrough the voltage range using the incremental voltages.

The scanned pattern and/or locations may be captured 116 by thecalibrated video camera. In some embodiments, a fluorescent plate may beprovided and the beam may be scanned to locations on the fluorescentplate so as to facilitate capture of the scanned pattern by the videocamera. The calibrated video camera may then capture electromagneticradiation reflected from the fluorescent plate in response to thescanned pattern. The pixels of the video camera which capture thereflected electromagnetic radiation may be used to define the physicallocations of the scanned XY pattern. The xy-scan device may then becalibrated by mapping the scanned physical XY locations to the definedcontrol parameters using a polynomial fit or a look up table.Accordingly control parameters of the xy-scan device may be correlatedto the pixels of the camera and the physical locations. In someembodiments, the voltages for actuating the xy-scan device may becorrelated with the physical locations.

In some embodiments, a z-scan device may be calibrated 106 to provide anoptimal z-axis laser beam focus at a plurality of depths. In someembodiments, control parameters may be defined for focusing theelectromagnetic radiation beam to a series of depth locations 120.Thereafter, the beam may be focused to the series of depths and the scandepths may be captured by the video camera or a confocal detector 122.The treatment space may then be mapped to the control parameters of thez-scan device 124.

In some embodiments, control parameters such as a voltage for actuatingthe z-scan device may be defined for focusing the electromagneticradiation beam to a series of depth locations. The electromagnetic beammay be projected toward an fluorescing plate so as to facilitateidentification of the focusing depth. As shown in FIG. 23 thefluorescing plate 2310 may be supported on a jack 2320 and the jack 2320may set the depth of the fluorescent plate 2310. Optionally, the jack2320 may be automated and driven to along a range of depths bycalibration software or hardware. The jack 2320 may have an adjustabletilt in XY to set the fluorescent plate 2310 perpendicular to the laserbeam. The video camera or a confocal detector can be used fordetermining the focal depth of the electromagnetic radiation beam. Inmany embodiments, the XY polynomial fit may be independent of Z depth.However, the XY polynomial fit can be a function of Z-depth in someembodiments.

FIG. 24A-24D illustrates another method of calibrating a laser systemwith a Z-depth. A laser system contact 2410 may be spaced a knowndistance from a plate 2420. In some embodiments, as shown in FIG. 24A, adisk 2430 with a known depth may be placed between the laser systemcontact 2410 and the plate 2420. The disk 2430 may have a depth of 4-15mm in some embodiments. Optionally, disk 2430 may have a depth of 6-10mm and preferably 8 mm. After positioning the laser system contact 2410a known distance from the plate 2420, the disk 2430 may be removed asillustrated in FIG. 24B. A fluid 2440, such as water, may then addedsuch that the fluid level increases by incremental amounts asillustrated in FIG. 24C and FIG. 24D. For example, in some embodiments,the fluid level may be increased by one mm increments. In between eachfluid level increase, the fluid level may be detected using imagingcomponents of the laser system, such as an OCT imaging system. In someembodiments the fluid level may be increased in three increments of onemm.

Other variations are within the spirit of the present invention. Thus,while the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

While certain illustrated embodiments of this disclosure have been shownand described in an exemplary form with a certain degree ofparticularity, those skilled in the art will understand that theembodiments are provided by way of example only, and that variousvariations can be made without departing from the spirit or scope of theinvention. Thus, it is intended that this disclosure cover allmodifications, alternative constructions, changes, substitutions,variations, as well as the combinations and arrangements of parts,structures, and steps that come within the spirit and scope of theinvention as generally expressed by the following claims and theirequivalents.

1.-26. (canceled)
 27. A method of calibrating a laser system with aZ-depth, comprising: placing a laser system contact at a predetermineddistance from a plate; placing a fluid on the plate between the plateand the laser system contact; incrementally adding the fluid on theplate to increase a fluid level by incremental amounts to a plurality ofknown fluid levels; at each of the plurality of known fluid levels,detecting the fluid level using an imaging system of the laser system;and correlating the fluid levels detected by the imaging system with theknown fluid levels.
 28. The method of claim 27, wherein the step ofplacing the laser system contact at the predetermined distance from theplate includes: placing a disk with a predetermined depth between thelaser system contact and the plate, the disk contacting the plate;positioning the laser system contact against the disk; and removing thedisk.
 29. The method of claim 28, wherein the disk has a depth of 4-15mm.
 30. The method of claim 28, wherein the disk has a depth of 6-10 mm.31. The method of claim 27, wherein the fluid level is increased by onemm increments.
 32. The method of claim 31, wherein the fluid level isincreased in three increments of one mm.
 33. The method of claim 27,wherein the fluid is water.
 34. The method of claim 27, wherein theimaging system of the laser system is an OCT (optical coherencetomography) imaging system.